RESUMO
@#Objective To screen the formulation of heat-resistant protective agent for live classic swine fever(CSF) vaccine in order to prolong the preservation time of vaccine under harsh conditions.Methods The heat-resistant protective agent prepared based on the formula containing gelatin,D-sorbitol,trehalose,D casein hydrolysate of different contents was mixed with the live virus antigen of CSF and then lyophilized.The finished products with qualified appearance were screened for routine detection and aging resistance test,and the over-dose(10 and 30 portions) of the products qualified in the aging resistance test were used to immunize piglets via subauricular neck,5 for each to evaluate the safety of the vaccines.Results Among the 6 batches of lyophilized live CSF vaccine,3 batches(20200301,20200302 and 20200303) met the requirements of the current Chinese Veterinary Pharmacopoeia.The lyophilized loss was within 0.04～0.33 titers,and the moisture contents were all less than 2%;20200301 and 20200302 batches of finished products passed the aging resistance test.No adverse clinical symptoms were observed in all piglets 30 min after vaccination;The body temperatures of piglets vaccinated with 10 and 30 doses of vaccine were normal for 14 d after vaccination.Conclusion The two formulations of heatresistant protective agent selected might be used for freeze-dried preparations of live CSF vaccine with good effect of aging resistance and safety to piglets.